Individual recognition of male Tawny owls (Strix aluco) using spectrograms of their territorial calls

Faced with the problem of mapping accurately the Tawny owl's territories, we used spectrographic analyses of the recorded territorial calls to distinguish the different individual males. From November 1986 to August 1988 we collected about 2000 hootings from different Tawny owls. The visual analysis of the spectrograms revealed a high degree of inter-individual variation and a certain amount of intra-individual variation in the song, so that we have submitted a sample of 140 calls of 17 identified individuals to univariate and multivariate analyses, in order to reach objective conclusions. Seven temporal parameters of the song were selected and measured. The coefficient of variation for each parameter and the test of homogeneity of variances between two series of calls of the same owl showed a stability over time of the selected parameters. On the other hand, the ANOVA test indicated that all the parameters of song varied significantly within the population and discriminant analysis provided a correct classification of 99.1% of the individual Tawny owls.